Cycles - and my poor little CPU

Yes, it’s true… I don’t have a fancy GPU… just the one on the motherboard.

So, I’ve been using Eevee for animated shorts… and am happy with the results.

But… it’s time. Time to try Cycles.

Since my render time will change from minutes to hours, I’m looking for wisdom.

I’m at 2.93. I’ve got Cycles set to 8 (yes, 8) samples. I’m rendering 3600 x 2400 frames… and am Happy with the results.

BUT ! ! ! My CPU is PEGGED at 100% during each (F12) render.

My question:

If I let it render 20, or 30 seconds at 30 frames/second… that’s hours of 100% CPU !

Will it set off my fire alarm?

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100% CPU load is normal. My CPU has been running 100% load continuously 1,5 years.

Just don’t use laptop for that. They are not designed for that kind of usage.


20 minutes render time for 5 frames.
Never mind.
Sticking with Eevee.

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Just for information, it is normal for decades that rendertime is something like two or three hours per frame. Except for high profile productions where one frame could take days or weeks from single computer.

Sure in small budget rendering we are talking rendertimes like 15-20min per frame and resolutions were back then 640x480 or 1280x720. But when GPU rendering was available and access to cheap renderfarms, rendertimes were cut to one minute per frame.

4min per frame in CPU is considered ultra fast rendering.

Just out of curiosity what is this for rendering so big. I have noticed that render times increase considerably when the frame is larger.

I recently rendered 1200 frames - 1080 x 720 - in Eevee at 10 samples. It took 20 minutes.

That’s 1 frame per second.

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I was experimenting with various sample settings and frame sizes in Cycles.

I was trying to eliminate pixelation. (or however you spell it)

Sure, Eevee is scanline renderer, similar rendering technology like game engines. Complex scenes in Eevee, like 256 samples can take minutes.

Trade-off to have 100x faster rendering is lost of true light bounces. Those need to be faked in Eevee.

The matter is how much temperature the laptop reach with 100% for hours. If you want to render in Cycles and even in Eevee invest in a laptop with a GPU.
GPU’s do not reach so much temperature in relation to CPU and are much faster - like 10x faster- so you will be shorter time at 100% GPU.
A RTX3060 is a good entry point.

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This can be solved when using Eevee. Where you got pixelation?

I would recommend to use renderfarm, own server or desktop computer. Laptops sucks to run 100% load for months. They are not designed for that.

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It seems to me that if the image is not the size you rendered at it looks distorted sometimes. So When you view it in blender if you frame it.

I render usually in my laptop without issue. A BMW27 like scene is rendered at 12-13 sec per frame.

Issue in laptops are that they got all dust inside when cooling starts and it easily shortens laptop usable life.

I don’t see any point of buying new laptop every two years. Better idea to put rendering in desktop/server/renderfarm and use laptop something like 8+ years.

This matters today more than decades ago because Moore’s law is slowing down. Six years newer hardware is not anymore 10x faster.

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I disagree. Laptops have been evolving very fast and i expect a big jump in next years. I have bought in 2009(i was bad in finances so i bought a cheap one), 2013 and 2021. Today CPU’s are already in 16000 in Cinebench R23 while mine is in 13000, RTX40xx is around the corner, and screens are getting better, pretty much covering the 100% sRGB today. 16Gb RAM are standard. If you have a huge project to make i agree you will need support but i can now start my projects well in my laptop.

I wrote this using laptop from year… 2013? And it has 16Gb memory. Nine years newer laptops are faster but difference is smaller than comparing laptops from year 2004.

I expect leap in efficiency/performance when they switch from x86 → ARM, optimize silicon area and integrating chips closer.

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16 Gb was not common in 2013, mine from that date also had 16Gb, but its GTX765 card can not work with Cycles and Davinci Resolve. Resolve needs W10 or W11 and encoding is super fast with current GPU that even goes to 100%, so GPU’s do much more today than in 2013 and i expect to do even more in the future

I think it is the integrating chips closer that makes CPU’s being worse regarding temperatures. My 3060 laptop consumption reached 133w, more 50w than the 5800H but the maximum temps are 20ºC less.

You really need to check this out…it has completely changed how I work with Blender and Cycles!

It is x86 architecture. Integrating chips closer reduces latency and power to require sending data to other parts of computer. And I don’t expect that architecture to last long in laptops.

Most power efficient system is integrating everything to same chip and sharing memory with GPU and CPU. It is mostly bandwidth limited. GPUs are long time done “everything” so to get more GPU power it is best to separate it from CPU and CPU ram, and try to connect GPU+VRAM directly to flash memory and avoid moving data first using CPU.